Employee Commuting Emissions: What Data Do You Actually Need?

Conversion factors are only useful if the underlying commute data is good

Last week, we wrote about the publication of the 2026 UK Government Greenhouse Gas Conversion Factors and how the relevant factors have already been incorporated into CalCommuter.

Those conversion factors are important. They provide the official assumptions used to convert activity data into greenhouse gas emissions estimates.

But they are only one part of the calculation.

To understand employee commuting emissions properly, organisations also need reliable activity data.

At the most basic level, that activity data is simple:

How many miles or kilometres are travelled by each mode of transport over the reporting period?

For example:

• miles travelled by car

• miles travelled by bus

• miles travelled by rail

• miles travelled by tram

• miles travelled by motorcycle

• miles travelled by walking or cycling, where relevant

• hours worked from home, where homeworking emissions are included

Once an organisation has that information, the relevant conversion factor can be applied to estimate emissions.

That is the minimum requirement.

But it is rarely the best way to collect the information.

The problem with asking employees to estimate mileage

In theory, an organisation could ask every employee:

“How many miles do you travel by car each week?”

or:

“How many miles do you travel by bus, rail or other modes each month?”

That would provide a direct input for the conversion factor calculation.

The problem is that many employees will not know the answer.

Some may know roughly how far they drive. Others may guess. Some may check Google Maps. Some may not. Rail distances can be even harder for individuals to estimate accurately unless they use a specialist tool or manually look up distances between stations.

The result can be inconsistent data.

That does not mean the data is useless. For a rough estimate, self-reported mileage may be better than having no data at all.

But if an organisation wants a more reliable commuting emissions baseline, it is usually better not to ask every employee to estimate the distance themselves.

Instead, the organisation can ask for the information needed to calculate distance more consistently.

That is where home location, worksite, mode and commute frequency become important.

A better approach: calculate the distance rather than asking people to guess

Rather than asking employees to estimate total weekly or monthly mileage, CalCommuter asks for practical information about the commute itself.

This usually includes:

• home postcode

• main worksite

• usual commute mode

• how often the employee commutes

• working from home pattern, where relevant

This means the employee does not need to know how many miles they travel by car, bus or train.

The platform can calculate the relevant distances and apply the appropriate emissions methodology.

This reduces guesswork.

It also improves the employee experience. The survey becomes easier to complete because employees are asked questions they are more likely to know the answer to.

Most people know where they live, where they work and how they normally travel.

Fewer people know their weekly mileage by mode.

Why the main worksite matters

For commuting emissions, the important destination is normally the employee’s main or usual worksite.

Many organisations have multiple worksites. Local authorities, NHS organisations, universities and large employers often operate across offices, depots, hospitals, campuses and satellite sites.

CalCommuter can support analysis across multiple worksites.

However, for an individual employee, the commute is normally assessed against their main worksite.

That distinction matters.

If an employee occasionally travels to another worksite as part of their job, that journey may be treated differently by the organisation. In many cases, travel to non-main worksites is more likely to sit within business travel processes rather than employee commuting.

Keeping this distinction clear helps avoid double counting and keeps commuting emissions analysis focused on the journey between home and the employee’s normal place of work.

Mode of transport: more than just “car” or “public transport”

To apply the right emissions factor, organisations need to understand how employees usually travel.

Common commute modes include:

• car or van

• car sharing

• bus

• rail

• tram or light rail

• motorcycle

• walking

• cycling

• working from home

• other or variable journeys

For most employees, the commute fits a main mode reasonably well.

That is important because it keeps the survey simple and the analysis consistent.

Vehicle information can make car emissions more accurate

For car and van commuters, vehicle information can significantly improve the accuracy of emissions estimates.

A generic car emissions factor may be suitable for a broad estimate, but it will not reflect the difference between different vehicles.

Even asking for fuel type and engine size can be difficult.

Many people know whether their car is petrol, diesel, hybrid or electric. Fewer people know the engine size or the precise category needed to select the most appropriate conversion factor.

CalCommuter takes a practical approach.

Where employees are willing and able to provide their vehicle registration number, the platform can use that to retrieve specific vehicle emissions information from DVLA data.

This supports a more accurate calculation than relying only on a generic car assumption.

It also feels more accurate to the individual employee. Their commute is being calculated based on their vehicle, rather than an average vehicle that may not reflect what they actually drive.

Where appropriate, a real-world uplift is then applied in line with the detailed UK Government conversion factor methodology.

Not everyone will provide a registration number. Some people may not want to. Others may not remember it when completing the survey.

That is fine.

In those cases, the calculation can fall back to average assumptions.

The objective is to balance accuracy with practicality.

For car and van commuting, it is also important to understand whether the journey is single occupancy or shared.

Where someone car shares, the number of people typically sharing the journey matters because the emissions can be allocated across the people travelling together rather than treated as if each person made a separate single-occupancy car journey.

What about mixed or variable commutes?

Some commutes do not fit neatly into one main mode.

An employee might sometimes drive and sometimes take the bus. Another might drive to a station and then take the train. Someone else might have a commute that varies depending on shift times, caring responsibilities or weather.

These cases matter, but they are usually a minority.

In CalCommuter, most employees can describe their commute using a main mode. For the small proportion of employees whose commute is genuinely variable or does not fit the standard options, the platform can ask for estimated mileage, journey time and cost.

That is less precise than calculating the distance automatically from a standard origin, destination and mode.

But it is still useful.

It also means those employees can still feel that their commute has been counted, without making the whole survey more complicated for everyone else.

The key point is proportionality.

It is better to calculate distances consistently for the majority of employees and use estimated inputs only where needed, rather than asking every employee to estimate mileage from the start.

Frequency matters more than full-time equivalent

Commuting emissions are driven by travel activity.

That means the number of commute journeys matters.

It is not enough to look only at full-time equivalent status.

For example, an employee who works two hours a day, five days a week, may represent a small full-time equivalent value. But they may still make five return commutes every week.

From a commuting emissions perspective, that frequency matters.

Similarly, someone working compressed hours, part-time, hybrid or shift patterns may have a commute profile that is not obvious from their contracted hours alone.

To calculate commuting emissions properly, organisations need to understand how often employees actually travel to their worksite.

Questions might include:

• how many days per week they usually commute

• whether they work from home

• whether their working pattern varies

• whether they are part-time, full-time or shift-based

• whether they attend the worksite regularly or only occasionally

This is particularly important when comparing emissions over time.

A reduction in commuting emissions may reflect a change in transport mode. But it may also reflect a change in working pattern.

Both matter.

Hybrid working means commute frequency and homeworking should be considered together

Hybrid working has changed how organisations need to think about commuting emissions.

An employee may have a long car commute but only travel to the office once or twice a week.

Another may live close to work but travel every day.

The emissions impact depends on both distance and frequency.

Homeworking can also form part of the wider picture. Fewer commute journeys may reduce travel emissions, but working from home can create additional emissions through domestic energy use.

That does not mean homeworking is automatically better or worse. It depends on the circumstances.

The important point is that organisations should understand the pattern.

If they only look at commute distance, they miss frequency.

If they only look at full-time equivalent status, they may miss the actual number of journeys.

If they only look at office attendance, they may miss the homeworking element.

A good approach considers how people actually work and travel.

Reporting is the starting point, not the end point

If an organisation only wants a commuting emissions number, the process can be fairly simple:

1. Understand distance travelled by mode.

2. Apply the relevant conversion factors.

3. Scale the result to the reporting period.

That can produce a baseline figure.

But for many organisations, collecting richer commuting data through a platform such as CalCommuter can do much more.

It can help sustainability teams understand Scope 3 emissions.

It can help transport teams identify realistic opportunities for mode shift.

It can help estates teams understand parking demand.

It can help HR teams support staff with commuting information during onboarding.

It can help wellbeing teams understand where commuting cost, time and stress may be affecting employees.

This matters because employee commuting is rarely just one team’s issue.

One person may be responsible for calculating the emissions figure. Another may be responsible for reducing those emissions. Another may be dealing with car parking pressure. Another may be thinking about staff wellbeing, recruitment or access to employment.

Good commute data can support all of those conversations.

Employees usually care most about cost and time

Emissions reporting is often most important to the organisation.

For individual employees, the most useful information is often more practical.

How much does my commute cost?

How long does it take?

How much do those realistic alternatives cost, and how long do they take?

Would another option save me money, time or stress?

Many people already know that cycling produces fewer emissions than driving.

Putting a precise emissions number against that may be useful, but it is not always the main factor that changes how someone thinks about their commute.

Cost, journey time, convenience and reliability are often more personally relevant.

That is why commuting emissions analysis should not be separated from wider workplace travel planning.

The emissions number matters.

But the opportunity to help people understand their options matters too.

What CalCommuter does

CalCommuter helps organisations understand employee commuting and homeworking emissions without relying on every employee to estimate mileage manually.

The platform collects practical commute information, calculates distances, applies appropriate emissions methodologies and provides evidence-based insight for employers.

Employees receive tailored commute plans showing the cost, duration and emissions of their current commute alongside realistic alternatives.

Employers receive insight into commuting emissions, homeworking emissions, mode share, geographic patterns and opportunities for action.

That means CalCommuter can support the baseline emissions calculation.

But the real value is what comes next.

It helps organisations understand how staff commute today, how they could travel tomorrow, and where practical opportunities for change may exist.